Ozone surprise.

Once again, an accidental discovery may have aided science. Following up on a puzzling observation made years ago, analytical chemist Steven Goheen and his team at the Pacific Northwest National Laboratory write in the February 2004 issue of Bioelectromagnetics that high-voltage electrical devices can, under certain conditions, indirectly generate high ozone levels in the presence of an animal or water. Ozone is a respiratory irritant that can reduce lung function, aggravate asthma, and trigger asthma attacks.

In an earlier study linked to an investigation of why negatively charged ions kill bacteria, Goheen found that discharging a negative ion source into a flask containing a little water created ozone in the neighborhood of 1,500 parts per billion (ppb)--vastly higher than the U.S. Environmental Protection Agency 8-hour standard of 80 ppb. To find out more about this quirk, Goheen and colleagues equipped an enclosed polycarbonate box with a stainless steel negative ion source--or corona discharge--in the roof, an exhaust tube in one side to monitor ozone, and a grounded wire mesh just above the floor. The corona discharge operated at a range of 5-10 kilovolts (kV), similar to that of certain high-voltage appliances such as negative ion generators. They either filled the bottom of the box with water or placed three rats in the dry box, then generated a corona discharge at 5, 7.5, or 10 kV, with the tip of the steel discharge rod kept at 1 or 8 centimeters (cm) from the rats' heads or the water.

With neither water nor rats in the box and the corona discharge on, ozone remained near its ambient level of about 15-20 ppb. With just water in the box, ozone rocketed to an average of 290 ppb. The increase was slightly less with the rats in the dry box, rising to about 255 ppb at 10 kV, with proportionately lower increases at lower voltages. The increases occurred only at a distance of 1 cm, not at 8 cm. In addition to increased ozone production, the rats froze in place when the discharge was on, but moved freely when it was off, for unknown reasons.

The team speculates that moisture and the sharp points on fur and whiskers may be key factors that spur the production of ozone. Other variables Goheen suggests exploring include alternative voltages and distances, pulsed discharges, number and mass of animals, length of exposure, creation of chemical species other than ozone, and spatial volume.

The findings are intriguing, but the short distance from the rod to the animals suggests to some critics that the phenomenon is unimportant, because the tested scenarios are unlikely to reflect real-world situations. Much more study of this issue is necessary before it can rise to the level of a serious public health concern, says Robert Kavet, electromagnetic field business area manager at the electric utility-funded Electric Power Research Institute.